The more servers that are added to a data centre, the more cooling that centre is likely to need. And the more cooling those servers require, the more "whoosh" is generated. Whoosh, for the uninitiated, is the annoying noise of fans and humming power supplies that can feel like a pressure in your head.
Data centre workers live with this noise. It's part of the job, part of the culture. But there may be reason to start giving the noise issue more attention: data centre consolidations and the adoption of high-density equipment - both big industry trends - are bringing more equipment and denser and hotter systems into data centres.
There's a dearth of scientific data assessing noise trends in data centres, its health consequences and the impact on productivity. Noise is simply taken for granted by data centre managers who spend little, if any, time measuring sound levels. For the most part, data centre workers just learn to deal with it.
"It's pretty loud, it's pretty stressful," said computer operator Bruno Skiba, who works at a financial services firm and wears ear protectors similar to those used on a firing range.
Noise, of course, varies from centre to centre, system to system. It's now fairly common for data centre workers to spend a lot of time off the data centre floor and manage systems in separate rooms. And on a system level, noise can vary. While some racks may have high-speed, whinny fans, some Itanium-based servers from Hewlett Packard have larger fans that are less noisy. Skiba's firm recently got a delivery of those quieter servers.
Taken in concert, the noise generated from all the equipment in a data centre can be distracting. That fact prompted data centre workers at C I Host, a Dallas-based hosting company, to get Bose noise-cancelling headphones to help make the work environment comfortable, said Christopher Faulkner, CEO at C I Host.
"The noise - the pressure on their head, if you will - is very distracting and causes serious issues with [workers] being able to concentrate and do their jobs," said Faulkner.
Faulkner said he's never measured the noise in his data centre, something that wouldn't be surprising to Tad Davies, executive vice president of the Brick Group, a St. Louis-based company that designs and builds data centres. Davies said he can recall only one IT manager who asked for sound level measurements. "It's been, universally, an issue that has not been brought up," he said.
Davies, without naming the customer, shared a schematic of the data centre showing the decibel levels taken in 12 different places in the facility. The lowest was 70 dB and the highest 79 dB. The highest levels were recorded near HVAC equipment. At these levels, you have to talk loudly to be heard, but they are considered safe levels under US Government standards.
By comparison normal conversation is about 60 dB; a power lawn mower is about 90 dB, a jet engine at takeoff, 140 dB, according to the US National Institute for Occupational Safety and Health. The US Government sets workplace standards for noise, and doesn't require action until workers are exposed to average noise levels of 85 dB or greater during an eight-hour day.
Dr. Peter Rabinowitz, a member of the American College of Occupational & Environmental Medicine's Sensory Perception Committee, said he is unaware of any data centre-specific research on noise. While OSHA sets standards for action, low frequency noise coming off fans and air handling systems can affect concentration and produce fatigue, he said.
"In general, I think people like to work in a fairly quiet workplace," said Rabinowtiz.
There is no single agreed-upon decibel level standard for protecting workers who must deal with the constant din of data centre noise. But if workplace noise reaches 85 decibels (dB) it triggers some steps under law in the US. By contrast, Europe's workplace protections begin at the 80dB level.
The question is: who's measuring? There is a dearth of studies on noise in the data centre, said Mark Stephenson, a senior research audiologist and coordinator National Institute of Occupational Safety & Health (NOISH) hearing research. NOISH is part of the U.S. centres for Disease Control and Prevention.
"I'm not aware of studies that have demonstrated that working in a data centre exposes you to hazardous noise," Stephenson said. "However, there certainly could be something out there.
"The trend toward larger and larger facilities would have a slow incremental increase in the noise level, so it's possible that something like [crossing the legal threshold for action] would creep up," said Stephenson.
If the noise level reaches 85dB over an eight-hour day, that should trigger some monitoring under Occupational Health and Safety Administration regulations. If noise levels hit 90dB then companies are required to take steps to protect workers' hearing.